1. Field of the Invention
The present invention relates to a method of communication on a multidrop bus of a magnetic resonance system, and, more particularly, it relates to a multidrop bus telegram adaptive protocol script (Adaptive Protocol Script For Telegram Over Multidrop Bus, abbreviated below to APSTOMB) communication method which is used in a magnetic resonance system.
2. Description of the Prior Art
Currently, in order to strictly maintain the operating environment of a scanner in a permanent-magnet magnetic resonance system, the usual practice is that many control channels or monitoring channels are used to effect regulation and state monitoring of physical parameters such as the magnet temperature, etc. for a monitoring target.
When there are different monitoring target circumstances, separate management using independent monitoring units is usually conducted in the system, since the monitored parameters needed for different monitoring targets vary, but there are the following drawbacks in this type of system:                It is difficult to obtain monitoring units possessing similar functions, and the system requires that many modules be managed, so making the cost high;        the increase of the modules leads to an increase of the complexity of failure modes, and so the cost of investigations into failure mode analysis (Failure Mode and Effects Analysis, FMEA), is increased;        the increase of hardware lowers the reliability of interrelations between components, and increases the hardware failure rate, so leading to a reduction of the mean time between failure (MTBF); and        since the communication protocols of the components of different companies differ, it is not possible to interconnect identical interfaces using a single bus, and it is difficult to achieve integration and embedding.        
In situations in which one and the same monitoring target has many monitoring channels, usually, regulators (or monitoring units) which are of the same type are employed. Since different monitoring points are necessarily subject to differences of monitoring parameter characteristics, the use of such independent monitoring modules has the following drawbacks:                High precision needs to be used for all the regulators (or monitoring units), and costs are very high;        some monitoring points are under quite highly sensitive control, and it is difficult to conduct work in coordination with other channels;        it is difficult for the functions of regulators (or monitoring units) to keep up with the technological innovations of products, and it is necessary to use new types of regulators (or monitoring units) in order to adapt to rapid edition upgrades; and        the type selection range for the regulators (or monitoring units) is small, and it is difficult to keep pace with the supply of spares and changes in commercial supplies.        
In some magnetic resonance systems a regulator (or monitoring unit) offline operation arrangement is used in order to avoid the above two drawbacks, but there are the following problems in such a system:                The regulators (or monitoring units) are not connected to the system and, in abnormal circumstances, it is not possible to ascertain in real time whether parameter changes have affected the image quality;        it is not possible for system maintenance staff to conduct highly efficient inspection and measurement work.        
There are also some systems in which, in order to avoid the above drawbacks, bus communication is not used, and a communication mode with arrival points reaching monitoring units at many points is used for regulators (or monitoring units), but there are still some problems with such a system:                The large number of physical connections increases the cost of the hardware; and        the large number of physical connections increases the hardware failure rate and reduces the mean time between failure.        